The invention relates to a T-shaped hose made of rubber or a rubber-like material with an embedded reinforcing inlay consisting of fabric or similar fiber structures with high loadability. More particularly, it relates to an improved T-shaped hose having a vulcanized hose branch secured with one end on an opening in the wall of a vulcanized main hose. The zone of connection is lined on the inner side of the hose branch with a sleeve made of polyamide or other viscously elastic plastic materials, and the sleeve rests on the cylindrical inner wall of the main hose with a flange-like edge.
T-shaped hoses made of rubber or rubber-like materials are increasingly needed in many technical fields, particularly in the auto industry, where such T-shaped hoses must meet high performance requirements. For example, such hoses have to be resistant to aging and heat, as well as to chemicals. Furthermore, embedded reinforcing inlays are expected to provide such hoses with the capability of receiving high pressures, i.e., high loadability.
In the past, various methods have been employed in the manufacture of such T-shaped hoses. According to the oldest manufacturing process, a T-shaped hose-connecting piece made of metal or plastic material is plugged or pushed over already-vulcanized hose sections (cf. German utility model No. 79 03 744; DE-OS No. 26 44 913; DE-OS No. 32 39 623).
In this regard, it is known from DE-OS No. 32 39 623 that instead of using hose clamps for securing or fastening the hoses, the individual hose sections are secured on the free ends of the manifold by vulcanization with an adhesion-imparting compound and a vulcanizable adhesive compound provided therebetween. However, this manufacture or structure of the T-shaped hose has the following drawbacks:
1. The dimensions of the parts used have to be matched with high accuracy, so that the hose sections can be easily pushed over the manifold, yet still assure a permanent bond between the manifold and the hoses.
2. The T-shaped tubular piece is disposed in the interior of the joined hose sections, after they have been pushed over the manifold, and presents a substantial flow resistance, which is undesirable.
3. The T-shaped manifold made of metal or plastic material and the hose made of rubber or a rubber-like material have different coefficients of expansion, so that when high temperature variations occur, stresses develop within the zone of the branching, leading to early wear of the T-shaped hose.
In order to avoid these drawbacks, a manufacturing process has been developed for T-shaped hoses which basically was carried out according to the following two variations A and B:
(A) A non-vulcanized hose branch is placed over a non-vulcanized or already-vulcanized hose with an opening. Subsequently, the T-shaped hose blank is vulcanized (cf. German utility model No. 74 30 853; DE-PS No. 24 43 824; DE-OS No. 25 51 386; DE-OS No. 31 22 212; DE-OS No. 31 51 640).
(B) The two prevulcanized hose parts are combined with each other by vulcanizing with the help of a non-vulcanized crude rubber part or a vulcanizable rubber compound or solution (cf. DE-AS No. 22 30 719; DE-OS No. 29 51 830; DE-PS No. 31 21 081; DE-PS No. 32 24 610).
The T-shaped hoses manufactured in accordance with these two variations do not exhibit the aforementioned drawbacks because the inner or internal branching piece is missing. However, breaks or cracks are more frequent within the zone of connection, a weak point in the T-zone of the hoses. From the great amount of work performed in this field, it appears that the T-shaped hoses manufactured according to variation A or B do not yet satisfy the highest requirements. Furthermore, the manufacturing processes according to A and B are still too costly, particularly in view of the fact that in most cases, the T-shaped hoses have to be manufactured by means of a mandrel in order to achieve a smooth inner wall. This, in turn, becomes a problem in particular if the hose parts extending from the zone of connection are relatively long and curved in complicated ways.
Now, a new method has been disclosed by the European Patent Application No. 88 571, which is carried out with the use of a sleeve, and which results in a T-shaped hose of the aforementioned type or design. With the T-shaped hose produced according to this method, the aforementioned problems are clearly less frequently encountered. However, this new process requires many production steps to produce a finished T-shaped hose from the hose blanks. Furthermore, this method also requires a number of manual working steps, which are frequently susceptible to error or defect sources, so that the reject rate is relatively high in the final quality control.
Accordingly, it is an object of the present invention to provide an improved T-shaped hose which can be more easily and reliably manufactured.